Metal marine buoys corrode in usage requiring periodic servicing. Such servicing involves locating leaks, repairing the leaks by sand blasting followed by welding and retesting to make sure the unit is leak free.
The repaired buoy is next painted the proper color and the submerged portion is given a coat of anti-fouling paint. The refurbished buoy is then returned to location. This process is repeated at regular intervals with the average time period between such refurbishing being about two years. Buoys that have suffered extensive corrosion are "surveyed out" of service.
The present invention provides a buoy repair method which greatly extends the life of metal buoys and decreases the frequency of repair. A bouy repaired by the method of our invention is essentially rust and corrosion proof, is unsinkable and is impervious to marine growth.
The buoy repair method of this invention involves the following steps: First, a large aperture or window is made in the shell of the buoy by cutting out a metal section. Then the interior of the hollow buoy is filled with urethane foam through the aperture. The third step involves welding back the cut-out metal section of the buoy shell after the interior is completely filled with urethane foam. Finally the metal exterior of the buoy is coated with a fiber glass-resin laminate and painted a color appropriate to its intended service.
It is known in the prior art to construct buoys or floats with inner cores of polyurethane foam. U.S. Pat. Nos. 3,121,889 and 3,728,749 describe such type buoys. It has also been known to construct buoy housings of fiber glass as is taught in U.S. Pat. No. 3,674,225. However, we are the first to devise a metal buoy repair procedure involving the integral steps of filling the buoy interior with urehtane foam and coating its exterior with a fiber glass-resin composition.
Metal buoys repaired by the process of this invention should be essentially maintenance free in service. They do not require cleaning as the fiber glass coating is rust and corrosion free and is impervious to marine growth. Repainting may be necessary at 12 to 15-year intervals for colors other than black or white, for which the interval between paintings will be of significantly longer duration.
Urethane foams used in the repair process of the invention are formed by the reactions of isocyanates, usually toluene di-isocyanate, with a polyol in the presence of a catalyst such as a mixture of an amine and an organo metallic compound such as tin alkanoate. More detailed information on the formation of urethane foams is found in the Encyclopedia of Chemical Technology, Second Edition, Volume 21, page 56 et seq. Urethane foams have a low water absorption and excellent buoyancy.
The use of fiber glass-resin laminates in marine applications is well known. Fiber glass laminate-coated boat hulls have practically preempted the small boat market because of their reduced maintenance costs. Detailed information on fiber glass-resin laminates is found in the aforementioned Encyclopedia, Volume 12, page 180 et seq.
Buoys repaired by the process of this invention only require periodic inspection of the mooring system. Their use involves significant savings in labor and maintenance.